Abstract: Objective To explore the correlation between postmortem interval （PMI） and five RNA markers of rat’s skin—β-actin, glyceraldehyde-3-phosphate dehydrogenase（GAPDH）, 18S ribosomal RNA（18S rRNA）, 5S ribosomal RNA （5S rRNA）, and microRNA-203 （miR-203）, at different temperatures. Methods Eighteen SD rats were randomly divided into three environmental temperature groups： 4 ℃, 15 ℃ and 35 ℃, respectively. Skin samples were taken at 11 time points from 0 h to 120 h postmortem. The total RNA was extracted from the skin samples and the five RNA levels were detected by real-time fluorescent quantitative PCR. Proper internal reference was selected by geNorm software. Regression analysis of the RNA markers was conducted by GraphPad software. Results 5S rRNA and miR-203 were most suitable internal references. A good linear relationship between PMI and RNA levels （β-actin and GAPDH） was observed in two groups （4 ℃ and 15 ℃）, whereas the S type curve relationship between the expression levels of the two markers （β-actin and GAPDH） and PMI was observed in the 35 ℃ group. The partial linear relationship between 18S rRNA and PMI was observed in the groups （15 ℃ and 35 ℃）. Conclusion Skin could be a suitable material for extracting RNA. The RNA expression levels of β-actin and GAPDH correlate well with PMI, and these RNA markers of skin tissue could be additional indice for the estimation of PMI.

Key words: forensic pathology, RNA, skin, temperature, postmortem interval, rats